1. Field of the Invention
The present invention relates generally to automotive navigation systems and, more particularly, to such a navigation system which processes both nationally broadcast traffic data and locally broadcast traffic data.
2. Description of Related Art
Automotive navigation systems have become increasing prevalent in automotive vehicles. Such navigation systems typically include a display screen mounted in the vehicle in a position visible to the driver. A roadmap is displayed on the screen from an internally contained map database and, by utilizing GPS to determine the position of the vehicle, also displays the position of the vehicle on the screen.
Many major roads, such as interstates and major arteries, include traffic sensors which detect the average vehicle speed at the position of the sensor on its given road as well as traffic events which potentially affect traffic flow. These traffic sensors transmit this traffic flow data to a central station which, after combining the received signals from the various traffic flow sensors across the country, transmits the combined traffic flow data to a geographic area. For example, in the United States, traffic flow data from the contiguous 48 states is continuously transmitted by satellite.
One disadvantage of the previously known navigation systems, however, is that the traffic data transmitted by satellite is necessarily limited to major roads and does not include traffic flow data for local roads in the geographic area. Consequently, these previously known navigation systems provide little or no information with respect to traffic flow along the local roads and are thus of limited utility for predicting local traffic flow and rerouting of the vehicle to a selected destination to minimize travel time.
A still further disadvantage of these previously known navigation systems is that such navigation systems only provide traffic flow data of the currently existing conditions. However, there are many non-traffic temporal events that can provide significant impact upon the future traffic flow conditions. For example, weather conditions, such as a predicted snowstorm, may significantly impact the traffic flow conditions during the expected travel of the vehicle from its current position and to the selected destination. Likewise, other temporal non-traffic events, such as sporting events, parades, and the like, may also impact the traffic flow along the anticipated route of the vehicle.
A still further disadvantage of these previously known navigation systems is that such navigation systems fail to use statistical data of traffic flow conditions along road segments in the locality frequently traveled by the vehicle as a function of time. For example, certain road segments may encounter excessive congestion during weekday rush hours, and yet have little or no traffic congestion during the non-rush hours or weekends. As such, these previously known navigation systems were unable to predict favorable routes for the vehicle to the desired destination while taking into account such statistical data.
A still further disadvantage of previously known navigation systems which do utilize statistical data of traffic flow conditions is that the statistical database is contained on non-writable persistent memory, such as a CD-ROM. However, there are many situations and events which alter the traffic flow conditions for particular road links. For example, road improvements or the construction of alternate roads for the particular road link may alter the traffic flow conditions for a particular road link. Similarly, an event such as the closing of a manufacturing facility around the road link will also modify the traffic flow conditions for that road link.